The present invention relates to a lap- or web-welded joint between a sheet-steel component and a light sheet metal component, in particular a sheet-aluminum component, in which the components are welded together with at least one hat-like steel clip part, having a bottom region which projects to the sheet-steel component through an opening arranged in the light sheet metal component, and a flange forming free rim resting on a free flat side of the light sheet metal component. The present invention also relates to a method for welding the two components to one another in which method the light sheet metal component in a region of the overlap with the sheet-steel component with at least one opening, inserting a clip part into the opening such that the clip part overlaps an exposed flat side of the light sheet metal component with a flange thereof which forms a free rim, and welding the clip part at a bottom thereof projecting into the opening to the sheet-steel component by electric resistance welding.
German Patent 940,267 describes welding of overlapping body parts, in which one body part is a non-load-bearing aluminum panel and the other body part is a steel frame part. Openings are arranged in the panel in the region of the overlap. Hat-shaped clip parts are inserted into the openings and are manufactured from a material, such as steel, capable of being welded to the frame part. The flange of the clip part, which forms the free rim, rests against the free flat side of the panel, the side remote from the frame part, while the bottom of the clip part, which is arranged in the opening, is welded to the frame part. The cross-section of the clip parts is matched to the clear width of the holes.
To ensure that the hat-shaped clip parts inserted into the holes in the panel and matched in cross-section to the hole in the known method can hold the panel in a defined position, the clip parts and the holes must be produced precisely. However, this is associated with a lot of effort in production and with additional costs. Moreover, the joint between the frame part and the panel is sensitive to the vibrations which arise during the operation of a motor vehicle because these vibrations lead to fatigue in the material of the clip part because of the continuous stressing and to the clip part bending at its flanks. This bending increases an already existing slight play between the clip part and the wall of the hole and, as a result, this joint loosens. Furthermore, because the joint between the panel and the frame part relies entirely on the elasticity of the steel clip part in the direction of the perpendicular to the surface of the overlap, the risk of this joint loosening increases further.
It is an object of the present invention to further improve the welded joint between the sheet-steel component and the sheet-aluminum component such that the joint is stronger and can be produced at lower cost which the overall workpiece can be produced with smaller tolerances following the joining process. A further object is to develop a method for welding the components to one another.
According to the present invention, the foregoing objects have been achieved, in the case of the component, by separating the clip parts, at least in certain areas, from the light sheet metal component by a gap and by arranging an adhesive, particularly a heat-activatable adhesive, in the gap. By way of the adhesive introduced into the gap, the two components are not only clamped in a direction perpendicular to the surface in the region of the overlap with one another but are additionally bonded. Moreover, the opening arranged in the sheet-aluminum component, and the clip part can be machined to wider tolerances, hence more cheaply, because the adhesive also joins the sheet-aluminum component and the sheet-steel component in a defined position parallel to the surface in the region of the overlap. It is particularly advantageous) if a heat-actuatable adhesive is used and is actuated either by the heat supplied during the welding of the clip part to the sheet-steel component or, in the case of components which are subsequently to be coated, by the heat supplied for baking the coating.